Enhanced functional connectivity in the reward circuitry in healthy adults with weekend catch-up sleep

We aimed to identify structural and functional changes in healthy adults with catch-up sleep (CUS), we applied seed-based functional connectivity (FC) analysis using resting-state functional magnetic resonance imaging (MRI). We hypothesized that deficits in reward processing could be a fundamental mechanism underlying the motivation of taking CUS. Then, 55 healthy adults voluntarily (34 with CUS and 21 without CUS) participated in this study. Voxel-based morphometry was performed to explore region of gray matter volume (GMV) difference between CUS and non-CUS groups. Between-group comparison of FC was then carried out using resting-state functional MRI analysis seeding at the region of volume difference. Moreover, the region of volume difference and the strength of FC were correlated with scores of questionnaires for reward-seeking behavior and clinical variables. CUS group had a higher reward-seeking tendency, and increased GMV in the bilateral nucleus accumbens and right superior frontal gyrus relative to non-CUS group. FC analysis seeding at the bilateral accumbens revealed increases of FC in the bilateral medial prefrontal cortex in CUS group compared to non-CUS group. The questionnaire scores reflecting the reward-seeking tendency were correlated with the FC strength between bilateral accumbens and medial prefrontal cortex. Our results indicate that CUS is associated with reward-seeking tendency and increased GMV and FC in regions responsible for reward network. Our findings suggest that enhanced reward network could be the crucial mechanism underlying taking CUS and might be implicated in the detrimental effects of circadian misalignment.